The present invention concerns the use of alpha-keto enamine derivatives as ingredients.
The Maillard reaction of L-proline with reducing monosaccharides has been extensively studied during the last two decades in order to gain insights into the formation of volatiles during thermal processing of cereal products (Tressl et al., J. Agric. Food Chem. 1985a, 33, 919-923; Tressl et al. J. Agric. Food Chem. 1985b, 33, 924-928; Tressl et al. J. Agric. Food Chem. 1985c, 33, 1132-1137; Helak et al. J. Agric. Food Chem. 1989a, 37, 400-404; Helak et al. J. Agric. Food Chem. 1989b, 37, 405-410; Huyghues-Despointes et al. J. Agric. Food Chem. 1994, 42, 2519-2524).
By application of the GC/olfactometry techniques such as Charm analysis (Roberts, D. D., Acree, T. In Thermally Generated Flavors; Parliment T. H., Morello M. J., McGorrin R., Eds.; ACS, Washington DC, 1994, 71-79) or aroma extract dilution analysis (AEDA)(Hofmann, T., Schieberle, P. J. Agric. Food Chem. 1998, 46, 2721-2726), the odor-active compounds could be successfully detected in solvent extracts of Maillard reaction systems composed of L-proline and reducing sugars. Amongst the volatiles detected, the popcorn-like smelling compounds 2-acetyl-1-pyrroline and 2-acetyltetrahydropyridine could be identified as the key contributors to the overall odor of thermally processed glucose/proline mixtures (Hofinann and Schieberle, J. Agric. Food Chem. 1998, 46, 2270-2277). Although the major part of the volatile reaction products formed during these roasting processes could be unequivocally shown by AEDA to have no odor activity, it cannot be excluded that some of these odorless compounds might evoke a certain taste sensation on the tongue such as, e.g., bitterness, heating or cooling. Consequently, the sensory attributes of such reaction products from reducing carbohydrates and proline were characterized.
By application of the recently developed taste dilution analysis (Hofmann, T. J. Agric. Food Chem. 1999, 47, 4763-4768) on HPLC fractions obtained from roasted glucose/proline mixtures two compounds could be detected, which showed an intense cooling effect on the tongue. These compounds were found to be formed in high concentrations when the hexose degradation product 2-hydroxy-3-methyl-2-cyclopenten-1-one was reacted in the presence of L-proline. After isolation by column chromatography both compounds could be obtained as pale-yellow oils with a purity of more than 99%. GC/MS and 1D- and 2D-NMR spectroscopy led to the unequivocal identification of these cooling compounds as 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC) and 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC). 
Although these compounds have been reported earlier by Tressl et al. (1985c) and Huyghues-Dispointes et al. (1994), these authors did not report on the cooling activity of these compounds when contacted with the tongue.
Besides 3-MPC and 5-MPC, we identified another cooling-active compound in the glucose/proline mixture, namely 2,5-dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF). 
3-MPC as well as 5-MPC could easily be synthesised by heating 2-hydroxy-3-methyl-2-cyclopenten-1-one and pyrrolidinium acetate in ethanolic solution or by dry-heating of 2-hydroxy-3-methyl-2-cyclopenten-1-one in the presence of proline. In analogy, DMPF could be obtained by reacting 4-hydroxy-2,5-dimethyl-3(2H)-furanone in the presence of pyrrolidinium acetate in ethanol or in the presence of proline under dry-heating conditions, respectively.
Japanese Patent 7242661 discloses DMPF as flavoring compound to impart flavour to wheat flour foods. This patent concerns flavor emitted from such foods that were just heated. Hence the patent deals with DMPF as a flavour precursor. GB Patent No. 1096427 concerns certain cyclopentanone derivatives as interesting compounds for perfumery. Certain alpha-keto enamines are claimed, but they are mentioned only as intermediates for the synthesis of other compounds.
Thus, it is desired to obtain an improved cooling agent, particularly for use as an ingredient in foodstuffs.
The invention relates to a food, cosmetic, or pharmaceutical composition including a compound of the general formula: 
wherein R1 includes N-Pyrrolidinyl, N-Pyridinyl, N-(amino-diethyl), N-(2-carboxy-pyrrolidinyl), N-(2-Methoxycarbonyl-pyrrolidinyl), or a combination thereof; R2 includes hydrogen, methyl, or a combination thereof; X includes methylene, ethylidene, 1-Propylidene, oxy radical, or a combination thereof; and Y includes methylene, ethylidene, 1-propylidene, oxy radical, ethan-1,2-diyl, ethen-1,2-diyl, propan-1,2-diyl, ethan-1-oxy-1-yl, or a combination thereof.
In a first embodiment, R1 includes N-pyrrolidinyl, R2 includes hydrogen, X includes methylene and Y includes ethylidene. In a second embodiment, R1 includes N-pyrtolidinyl, R2 includes methyl, X includes oxy radical and Y includes methylene. In a third embodiment, R1 includes N-Pyrrolidinyl, R2 includes methyl, X includes methylene and Y includes oxy radical. In a fourth embodiment, R1 includes N-Pyrrolidinyl, R2 includes methyl, X includes ethylidene and Y includes oxy radical. In a preferred embodiment, the compound includes at least one of 3-Methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC), 5-Methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC), 3-Methyl-2-(1-piperidinyl)-2-cyclopenten-1-one (3-MPipC), 5-Methyl-2-(1-piperidinyl)-2-cyclopenten-1-one (5-MPipC), 3-Methyl-2-diethylamino-2-cyclopenten-1-one (3-MDeaC), 5-Methyl-2-diethylamino-2-cyclopenten-1-one (5-MDeaC), 3-Methyl-2-diethylamino-2-cyclopenten-1-one (3-MDeaC), 5-Methyl-2-diethylamino-2-cyclopenten-1-one (5-MDeaC), 3-Methyl-2-(2-carboxy-1-pyrrolidinyl)-2-cyclopentene-1-one (3-MProC), 5-Methyl-2-(2-methoxycarbonyl-1-pyrrolidinyl)-2-cyclo-pentene-1-one (5-MMeproC), 5-Ethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-EPC), 3,5-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3,5-DMPC), 3,4-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3,4-DMPC), 4,5-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (4,5-DMPC), 3-Methyl-2-(1-pyrrolidinyl)-2-cyclohexen-1-one (3-MPCH), 6-Methyl-2-(1-pyrrolidinyl)-2-cyclohexen-1-one (6-MPCH), 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF), 5-Methyl-4-(1-pyrrolidinyl)-3(2H )-furanone (MPF), 4,5-Dimethyl-3-(1-pyrrolidinyl)-2(5H)-furanone (2(5H)-DMPF), 4-Methyl-3-(1-pyrrolidinyl)-2(5H)-furanone (2(5H)-MPF). In a more preferred embodiment, the compound includes 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone, 4,5-Dimethyl-3-(1-pyrrolidinyl)-2(5H)-furanone, 4-Methyl-3-(1-pyrrolidinyl)-2(5H)-furanone, or a combination thereof.
In one embodiment, the food composition includes at least one of chocolate, ice-cream, beverages, sugar confectionery, or petfood. In another embodiment, the cosmetic composition includes a topically administered cosmetic composition. In yet another embodiment, the perfume composition includes alcohol or water, or both. In any of these embodiments, the amount of the compound of formula (A) alone or in combination includes from about 0.01 mg/kg to 3000 mg/kg of the total composition. In general, the compound of formula A is present in an amount sufficient to impart a cooling effect.
This cooling effect is preferably accomplished with little or no detectable odor. Thus, in one embodiment, the compound has a cooling threshold to odor threshold ratio less than that of menthol. In a preferred embodiment, the ratio is less than about 3.
The invention also relates to a food product including the compounds and compositions including such compounds. In a preferred embodiment, the composition is completely free of mint-odor and optionally includes a fruity or brown flavor or odor. In one embodiment, the food product is a confectionery product or a malted beverage.
In one embodiment, the invention relates to a cosmetic product including the composition, while in another embodiment the invention relates to a perfume including the composition of the invention.
The invention also relates to a method of cooling a consumer""s skin or mouth by contacting an effective amount of the composition to the consumer""s skin or mouth to provide a cooling effect.
The present invention advantageously provides a group of compounds having excellent characteristics when used as an ingredient, more particularly as a cooling agent in foods, cosmetics, or perfumes. In contrast to menthol, which exhibits a strong mint-like odor, the compounds of the invention possess noxe2x80x94or at most a faintxe2x80x94odor and do not substantially modify the aroma of a food or other compositions in which they are included. The compounds of the invention include those of the general formula: 
alone or in combination, as an ingredient for food, cosmetic, pharmaceutical and perfume compositions, wherein R1 includes N-Pyrrolidinyl, N-Pyridinyl, N-(amino-diethyl), N-(2-carboxy-pyrrolidinyl), N-(2-Methoxycarbonyl-pyrrolidinyl), or a combination thereof. R2 includes hydrogen, methyl, or a combination thereof. X includes methylene, ethylidene, 1-Propylidene, oxy radical, or a combination thereof. Y includes methylene, ethylidene, 1-Propylidene, oxy radical, ethan-1,2-diyl, ethen-1,2-diyl, propan-1,2-diyl, ethan-1-oxy-1-yl, or a combination thereof.
In the present specification, xe2x80x9calonexe2x80x9d means that only one compound of general formula (A) can be used. But, it is also possible according to the invention, to use several different types of compounds of general formula (A) in the same composition.
In a first preferred embodiment, R1 includes N-Pyrrolidinyl, R2 includes hydrogen, X includes methylene and Y includes ethylidene (5-MPC). In a second preferred embodiment, R1 includes N-Pyrrolidinyl, R2 includes Methyl, X includes Oxy radical and Y includes methylene (MPF). In a third preferred embodiment, R1 includes N-Pyrrolidinyl, R2 includes methyl, X includes methylene and Y includes Oxy radical (4-methyl-3-(1-pyrrolidinyl)-2(5H)-furanone, 2(5H)MPF). In a fourth preferred embodiment of the general compound of the invention, R1 includes N-Pyrrolidinyl, R2 includes methyl, X includes ethylidene and Y includes Oxy radical (4,5-dimethyl-3-(1-pyrrolidinyl)-2(5H)-furanone, 2(5H)DMPF). Preferred compounds of the invention include at least one of 3-Methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC), 5-Methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC), 3-Methyl-2-(1-piperidinyl)-2-cyclopenten-1-one (3-MPipC), 5-Methyl-2-(1-piperidinyl)-2-cyclopenten-1-one (5-MPipC), 3-Methyl-2-diethylamino-2-cyclopenten-1-one (3-MDeaC), 5-Methyl-2-diethylamino-2-cyclopenten-1-one (5-MDeaC), 3-Methyl-2-diethylamino-2-cyclopenten-1-one (3-MDeaC), 5-Methyl-2-diethylamino-2-cyclopenten-1-one (5-MDeaC), 3-Methyl-2-(2-carboxy-1-pyrrolidinyl)-2-cyclopentene-1-one (3-MProC), 5-Methyl-2-(2-methoxycarbonyl-1-pyrrolidinyl)-2-cyclo-pentene-1-one (5-MMeproC), 5-Ethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-EPC), 3,5-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3,5-DMPC), 3,4-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3,4-DMPC), 4,5-Dimethyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (4,5-DMPC), 3-Methyl-2-(1-pyrrolidinyl)-2-cyclohexen-1-one (3-MPCH), 6-Methyl-2-(1-pyrrolidinyl)-2-cyclohexen-1-one (6-MPCH), 2,5-Dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF), 5-Methyl-4-(1-pyrrolidinyl)-3(2H)-furanone (MPF), 4,5-Dimethyl-3-(1-pyrrolidinyl)-2(5H)-furanone (2(5H)-DMPF), 4-Methyl-3-(1-pyrrolidinyl)-2(5H)-furanone (2(5H)-MPF).
In the case of a food composition, preferred foods include chocolate, ice-cream, beverages, sugar confectionery, and petfood.
In the case of a cosmetic composition, the compounds can be used in any topically applied cosmetic compositions.
In the case of a perfume composition, the compounds of the invention can be used in alcohol-based or aqueous-based compositions.
The amount of the compound of general formula (A), alone or in combination, is from about 0.01 mg/kg to 3000 mg/kg, of the composition. In one embodiment, the amount of compound is from about 0.05 to 500 mg/kg, while in another embodiment, the amount of compound is from 01. to 50 mg/kg. As already mentioned above, the above mentioned compounds of general formula (A) are used for the cooling effect they can induce to the compositions where they are introduced.
General Procedure to Synthesize Compounds of Formula (A)
An ethanolic solution (e.g., 600 mL) of a cyclic enolone compound (e.g., 100 mmol) may be refluxed in the presence of equimolar amounts (e.g., 400 mmol) of an amino compound (e.g., pyrrolidine) and acetic acid for several hours (e.g., 1-5 h). After cooling to room temperature, the solvent may be removed in vacuo and the residue may be taken up in water. The pH may be adjusted to 10 with a sodium hydroxide solution (e.g., 30% in water). The solution may then be extracted with an organic solvent (e.g. diethyl ether), the combined organic layers washed with an aqueous solution of sodium carbonate (e.g., 200 mL; 0.5 mol/L), dried over sodium sulphate and then freed from solvent in vacuo. The target compounds may further be purified by column chromatography on aluminium oxide (basic, activity III-IV, Merck, Darmstadt, Germany). Chromatography may be performed using various organic solvents in different ratios such as for example hexane (e.g., 200 ml), hexane/diethyl ether (e.g., 7:3, 400 ml), hexane/diethyl ether (e.g., 3:7, 400 ml), and diethyl ether (e.g., 400 ml). The fraction obtained with diethyl ether may be freed from solvent in vacuo affording the target compound. The compounds in Table 1 can be synthesized according to this general procedure.
Syntheses of 5-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (5-MPC) and 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC)
1. From 2-hydroxy-3-methyl-2-cyclopenten-1-on (cyclotene) and pyrrolidinium acetate in ethanol A solution of cyclotene (100 mmol), pyrrolidine (400 mmol) and acetic acid (400 mmol) in ethanol (600 mL) was refluxed for 2 h. After cooling to room temperature, the solvent was removed in vacuo, the residue was taken up in water (300 mL) and the pH was adjusted to 10 with sodium hydroxide solution (30% in water). The solution was then extracted with diethyl ether (5xc3x97150 mL), the combined organic layers were washed with an aqueous solution of sodium carbonate (200 mL; 0.5 mol/L), dried over Na2SO4 and then freed from solvent in vacuo. The residual oil was dissolved in pentane/ethyl ether (6/4, v/v; 10 mL) and then applied onto a column (30xc3x97500 mm) filled with a slurry of aluminium oxide (basic, activity III-IV, Merck, Darmstadt, Germany) in pentane. Chromatography was performed using pentane (300 mL; fraction A), pentane/diethyl ether (9/1, v/v; 300 mL; fraction B), pentane/diethyl ether (8/2, v/v; 300 mL; fraction C), pentane/diethyl ether (7/3, v/v; 300 mL; fraction D), pentane/diethyl ether (6/4, v/v; 300 mL; fraction E), followed by pentane/diethyl ether (5/5, v/v; 300 mL, fraction F). Fraction B containing 5-MPC (1.65 g, 10% in yield) and fraction D containing 3-MPC (1.32 g, 8% in yield) were collected and freed from solvent under vacuum affording the target compounds as pale-yellow oils. 
Synthetic preparation of 3-methyl-2-(1-pyrrolidinyl)-2-cyclopentene-1-one (3-MPC) and 5-methyl-2-(1-pyrrolidinyl)-2-cyclopentene-1-one (5-MPC)
2. From 2-hydroxy-3-methyl-2-cyclopenten-1-on (cyclotene) and proline dry-heated on aluminium oxide. A mixture of cyclotene (100 mmol) and proline (100 mmol) was ground with aluminium oxide (20 g, basic, activity III-IV) and then dry-heated for 10 mm at 180xc2x0 C. The mixture was suspended in water (100 mL) filtered, the pH was adjusted to 10 with sodium hydroxide solution (30% in water) and then extracted with diethyl ether. The work-up of the reaction mixture was performed following the procedure detailed above for the cyclotene/pyrrolidinium acetate mixture. The target compounds 5-MPC (120 mg) and 3-MPC (33 mg) were obtained as pale-yellow oils.
Spectroscopic Data
3-MPC:
MS (EI): 165 (100; [M]+), 164 (47), 137 (34), 136 (38), 122 (53), 109 (136), 108 (43), 94 (27), 81 (26), 67 (21), 41 (27).
1H NMR (360 MHz; CDCl3, COSY, TOCSY): xcex41.77-1.81 (m, 2xc3x972H, CH2), 2.13 (s, 3H, CH3), 2.34-2.35 (m, 2H, CH2), 2.39-2.41 (m, 2H, CH2), 3.40-3.44 (m, 2xc3x972H, CH2).
13C NMR (360 MHz; CDCl3; DEPT, HMQC, HMBC): xcex417.8 [CH3], 24.9 [2xc3x97CH2], 30.0 [CH2], 34.1 [CH2], 49.5 [2xc3x97CH2], 143.7 [C], 145.9 [C], 205.9 [CO].
5-MPC:
MS (EI): 165 (100; [M]+), 164 (32), 150 (26), 137 (22), 136 (37), 122 (87), 108 (34), 95 (34), 94 (31), 70 (21), 67 (24), 54 (24), 41 (25).
1H NMR (360 MHz; CDCl3, COSY, TOCSY): xcex41.16-1.18 (d, 3H, J=7.5 Hz, CH3), 1.82-1.88 (m, 2xc3x972H, CH2), 2.06-2.11 (dd, J=17.7, 2.2 Hz, 1H, CHaH), 2.35-2.43 (m, 1H, J=7.5, 2.2; CH), 2.71-2.78 (dd, J=17.7, 3.1 Hz, 1H, CHHb), 3.22-3.33 (m, 2xc3x972H, CH2), 5.82-5.83 (t, J=3.1 Hz, 1H, CH).
13C NMR (360 MHz; CDCl3; DEPT, HMQC, HMBC): xcex416.5 [CH3], 24.8 [2xc3x97CH2], 32.6 [CH2], 40.2 [CH], 48.1 [2xc3x97CH2], 123.6 [CH], 146.7 [C], 207.4 [CO].
Synthesis of 5-methyl-4-(1-pyrrolidinyl)-3(2H)-furanone (MPF)
1. From xylose and pyrrolidine. A solution of xylose (0.1 mol) and pyrrolidine (0.1 mol) in methanol (90 ml) was refluxed for 3 h, then, acetic acid (0.1 mol) was added and heating was continued for additional 2 h. After cooling, the solvent was removed in vacuo, the residue was taken up in water (100 ml), extracted with ethyl acetate (100 ml, 5 times), and the combined organic layers were extracted with aqueous 0.1M sodium hydroxide solution (3xc3x9750 ml), the organic phase was dried (sodium sulphate) and fractionated by column chromatography using aluminium oxide (basic, activity III-IV; Merck, Darmstadt, Germany) conditioned in n-hexane. Chromatography was performed using hexane (200 ml), followed by hexane/diethyl ether 7:3 (400 ml), 3:7 (400 ml), and diethyl ether (400 ml). The fraction obtained with diethyl ether was freed from solvent in vacuo affording the target compound MPF (0.9 mmol; 0.9%) as colorless oil with a purity of more than 99%.
2. From 4-hydroxy-5-methyl-3(2H)-furanone and pyrrolidine. A mixture of 4-hydroxy-5-methyl-2H-furan-3-one (10 mmol), pyrrolidine (20 mmol) and acetic acid (20 mmol) in methanol (50 ml) was refluxed for 3 h. After cooling, the solvent was removed in vacuo, the residue was taken up in H2O (100 ml), extracted with ethyl acetate (100 ml, 5 times), and the combined organic layers were extracted with aqueous 0.1M sodium hydroxide solution (3xc3x9750 ml), the organic phase was dried (sodium sulphate) and fractionated by column chromatography as detailed above. The target compound MPF (0.5 mmol; 5% yield) was obtained as colorless oil with a purity of more than 99%.
Spectroscopic data of MPF
GC/MS (EI): 42 (100), 167 (95), 54 (93), 96 (76), 124 (74)
1H NMR (360 MHz; CDCl3, COSY, TOCSY): 1.82 (m, 2xc3x972H, CH2), 2.23 (s, 3H, CH3), 3.11 (m, 2xc3x972H, CH2), 4.38 (s, 2H, CH2)
13C-NMR (360 MHz; CDCl3): 14.2 (CH3), 24.7 (2xc3x97CH2), 50.6 (2xc3x97CH2), 72.9 (CH2), 126.3 (C), 183.0 (C), 198.9 (CO)
Syntheses of 4,5-Dimethyl-3-(1-pyrrolidinyl)-2(5H)-furanone [2(5H)DMPF]
1. From 3-Hydroxy-4,5-dimethyl-2(5H)-furanone and pyrrolidium acetate in ethanol. A solution of 3-hydroxy-4,5-dimethyl-2(5H)-furanone (10 mmol), acetic acid (10 mmol) and pyrrolidine (10 mmol) in ethanol (50 mL) were refluxed for 3 h. After cooling to room temperature, the solvent was removed in vacuo and the residue was taken up in water (25 mL). The solution was then extracted with diethyl ether (5xc3x9710 ml), the combined organic layers were dried over sodium sulfate and then freed from solvent in vacuo. The residual oil was dissolved in pentane/diethyl ether (4/1, v/v; 5 mL) and then applied onto a column (30xc3x97500 mm) filled with a slurry of aluminium oxide (basic, activity III-IV, Merck, Darmstadt, Germany) in pentane. Chromatography was performed using pentane (300 mL; fraction A), pentane/diethyl ether (9/1, v/v; 400 mL; fraction B), pentane/diethyl ether (80/20, v/v; 400 mL; fraction C), pentane/diethyl ether (70/30, v/v; 400 mL; fraction D), pentane/diethyl ether (60/40, v/v; 400 mL; fraction E). Fraction E containing 2(5H)-DMPF (0.64 g, 36% in yield) was collected and freed from solvent under vacuum affording the target compounds a colorless oil.
Spectroscopic Data of 2(5H)-DMPF
MS (EI): 181 (82; [M]+), 166 (76), 138 (28), 136 (49), 122 (100), 110 (74), 108 (93), 94 (37), 82 (36), 68 (26), 55 (43), 54 (26), 53 (24), 43 (31), 41 (44).
1H NMR (360 MHz; CDCl3, COSY, TOCSY): xcex41.35-1.36 (d, 3H, J=6.6 Hz, CH3), 1.79-1.86 (m, 2xc3x972H, CH2), 2.03 (s, 3H, CH3), 3.47-3.57 (m, 2xc3x972H, CH2), 4.66-4.72 (q, 1H, J=6.6 Hz, CH).
13C NMR (360 MHz; CDCl3; DEPT, HMQC, HMBC): xcex411.8 [CH3], 19.2 [CH3], 24.9 [2xc3x97CH2], 49.3 [2xc3x97CH2], 78.0 [CH], 128.7 [C], 130.5 [C], 170.4 [CO].
Syntheses of 4-Methyl-3-(1-pvrrolidinyl)-2(5H)-furanone [2(5H)-MPF]
1. From 4-Methyl-dihydro-furan-2,3-dione and pyrrolidium acetate in ethanol. A solution of 4-methyl-dihydro-furan-2,3-dione (100 mmol, prepared according to Fleck et al., Helv. Chim. Acta 1950, 33, 130), acetic acid (100 mmol) and pyrrolidine (100 mmol) in ethanol (225 mL) was refluxed for 2,5 h. After cooling down to room temperature, the solvent was removed in vacuo and the residue was taken up in water (200 mL). The solution was then extracted with diethyl ether (5xc3x97100 ml), the combined organic layers were dried over sodium sulphate and then freed from solvent in vacuo. The residual oil was dissolved in pentane/diethyl ether (3/2, v/v; 10 mL) and then applied onto a column (30xc3x97500 mm) filled with a slurry of aluminium oxide (basic activity III-IV, Merck, Darmstadt, Germany) in pentane. Chromatography was performed using pentane (300 mL; fraction A), pentane/diethyl ether (9/1, v/v; 400 mL; fraction B), pentane/diethyl ether (80/20, v/v; 400 mL; fraction C), pentane/diethyl ether (70/30, v/v; 400 mL; fraction D), pentane/diethyl ether (60/40, v/v; 400 mL; fraction E), pentane/diethyl ether (50/50, v/v; 400 mL; fraction F). Fraction F containing 2(5H)-MPF (2.25 g, 14% in yield) was collected and freed from solvent under vacuo affording the target compound as a colorless oil.
Spectroscopic Data of 2(5H)-MPF
MS (El): 167 (94; [M]+), 166 (63), 139 (58), 138 (45), 122 (93), 120 (43), 111 (54), 110 (46), 108 (32), 95 (26), 94 (100), 82 (25), 81 (24), 80 (23), 68 (67), 67 (21), 55 (36), 54 (27), 53 (23), 41 (58).1H NMR (360 MHz; CDCl3, COSY, TOCSY): xcex41.80-1.86 (m, 2xc3x972H, CH2), 2.09 (s, 3H, CH3), 3.49-3.54 (m, 2xc3x972H, CH2), 4.53 (s, 2H, CH2). 13C NMR (360 MHz; CDCl3; DEPT, HMQC, HMBC): xcex412.4 [CH3], 25.1 [2xc3x97CH2], 49.5 [2xc3x97CH2], 71.7 [CH2], 124.3 [C], 130.7 [C], 171.6 [CO].
Sensory Analyses
Prior to sensory analysis, the purity of the synthetic taste compounds was checked by GC/MS. Determination of the cooling, as well as the aroma threshold, of the compounds was performed by trained panelists. Nasal odor thresholds (Guth, H.; Grosch, W. J. Am. Oil Chem. Soc. 1993, 70, 513-518), as well as cooling thresholds, were determined by triangle tests using tap water as the solvent. The samples were presented in order of increasing concentrations and the threshold values evaluated in three separate sessions were averaged. The values between individuals and separate sessions differed by not more than one dilution step.
The results of the sensory analyses are summarized in Table 2. Besides menthol, 5-MPC, 2(5H)-DMPF, MPF and 2(5H)-MPF had the lowest cooling threshold. Comparison of the odor threshold concentrations revealed the lowest value for menthol, which elicited a strong mint-like aroma, whereas the novel cooling agents showed significantly higher odor thresholds. Calculating the ratio of cooling threshold to odor threshold clearly demonstrated that the invention compounds, possessing no odor or only a faint odor, can be used as cooling compounds without imparting a strong odor. In comparison, for menthol the odor threshold is lower by a factor of 9.5, thereby, indicating that it is hardly possible to evoke a cooling effect in a product with menthol without having a significant mint-like odor. These data also show that by using the novel cooling compounds, it is now possible to evoke certain cooling effects during consumption of non-mint food compositions such as, confectionery products, malted beverages, and fruity or brown flavours. Especially 2(5H)-DMPF, MPF and 2(5H)-MPF have a much lower ratio of cooling threshold to odor threshold as compared to menthol and are, therefore, very efficient cooling substances.
In an additional experiment, the cooling thresholds of 3-MPC, 5-MPC, MPF, 2(5H)-MPF and 2(5H)-DMPF have been determined in chocolate. As given in Table 3, also in chocolate, 2(5H)-MPF was evaluated with the lowest cooling threshold of about 0.25 mg/100 g to 0.5 mg/100 g, whereas the 5-MPC showed an 8-fold higher cooling threshold. The ratio for compounds of the invention is typically less than that of menthol, preferably less than 9, more preferably less than about 3. In other embodiments, the cooling threshold to odor threshold ratio is less than about 1 or less than about 0.1.
Identification of 5-methyl-2-(1-pvrrolidinyl)-2-cyclopenten-1-one (5-MPC), 3-methyl-2-(1-pyrrolidinyl)-2-cyclopenten-1-one (3-MPC) and 2,5-dimethyl-4-(1-pyrrolidinyl)-3(2H)-furanone (DMPF) in Roasted Malt
Dark malt (50 g, Caraffa special) was frozen in liquid nitrogen and then ground in a mortar. The powder was then stirred overnight with dichloromethane (2xc3x97400 mL). The combined organic layers were then concentrated to about 50 mL in vacuo and the volatile fraction of the malt components were then isolated by high-vacuum distillation at 25xc2x0 C. The distillate obtained was concentrated to about 1 mL and then fractionated by column chromatography (0.9xc3x97100 mm) on aluminium oxide (basic, activity III-IV, Merck, Darmstadt, Germany), which was conditioned in pentane. Chromatography was performed using pentane (100 mL; fraction A), pentane/diethyl ether (9/1, v/v; 100 mL; fraction B), pentane/diethyl ether (8/2, v/v; 100 mL; fraction C), pentane/diethyl ether (7/3, v/v; 100 mL; fraction D), pentane/diethyl ether (6/4, v/v; 100 mL; fraction E), pentane/diethyl ether (4/6, v/v; 100 mL; fraction F), pentane/diethyl ether (2/8, v/v; 100 mL; fraction G), followed by diethyl ether (100 mL, fraction H). Fraction B, fraction D and fraction G, respectively, were collected and analysed by GC/MS. By comparison of the retention times as well as mass spectra (EI, CI) with those obtained from the synthetic reference compounds, 5-MPC (101.3 xcexcg/Kg) could be identified in fraction B, 3-MPC (9.4 xcexcg/Kg) in fraction D and DMPF (11.5 xcexcg/Kg) in fraction G.